Method and apparatus for processing data blocks during soft handover

ABSTRACT

A method and apparatus for processing data blocks during soft handover. The apparatus may be a wireless communication system including at least two enhanced uplink soft handover (EU-SHO) Node-Bs and a radio network controller (RNC). Each Node-B decodes a received data block and forwards the decoded data block to the RNC. If the RNC receives at least one copy of a successfully decoded data block, the RNC uses a re-ordering function entity to process the copy of the successfully decoded data block to support in-sequence delivery to higher protocol layers. If the RNC receives more than one copy of a successfully decoded data block, the RNC discards the extra successfully decoded data block copies. The RNC is either a serving-RNC (S-RNC) or a controlling-RNC (C-RNC). Each Node-B includes a medium access control (MAC) entity that handles enhanced uplink dedicated channel (EU-DCH) functionalities.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/517,779, filed Nov. 5, 2003, which isincorporated by reference as if fully set forth herein.

FIELD OF THE INVENTION

The present invention relates to the field of wireless communications.More specifically, the present invention relates to processing datablocks in a multi-cell wireless communication system, such as afrequency division duplex (FDD) or time division duplex (TDD) system.

BACKGROUND

Methods for improving uplink coverage, throughput and transmissionlatency are currently being investigated in third generation partnershipproject (3GPP) in the context of the Release 6 (R6) universal mobiletelecommunications system (UMTS) study item “FDD uplink enhancements”.

It is widely anticipated that in order to achieve these goals, Node-B(base station) will take over the responsibility of scheduling andassigning uplink resources (physical channels) to users. The principleis that Node-B can make more efficient decisions and manage uplink radioresources on a short-term basis better than the radio network controller(RNC), even if the RNC retains coarse overall control. A similarapproach has already been adopted in the downlink for Release 5 (R5)high speed downlink packet access (HSDPA) in both UMTS FDD and TDDmodes.

It is also envisioned there could be several independent uplinktransmissions processed between a wireless transmit/receive unit (WTRU)and a universal terrestrial radio access network (UTRAN) within a commontime interval. One example of this would be medium access control (MAC)layer hybrid automatic repeat request (HARQ) or simply MAC layerautomatic repeat request (ARQ) operation where each individualtransmission may require a different number of retransmissions to besuccessfully received by UTRAN. To limit the impact on systemarchitecture, it is expected that protocol layers above the MAC shouldnot be affected by introduction of the enhanced uplink dedicated channel(EU-DCH). One requirement that is introduced by this is the in-sequencedata delivery to the radio link control (RLC) protocol layer. Therefore,similar to HSDPA operation in the downlink, a UTRAN re-ordering functionis needed to organize the received data blocks according to the sequencegenerated by the WTRU RLC entity.

A soft handover macro-diversity operation requires centralized controlof uplink transmissions in each cell within an active set. The activeset may include a plurality of Node-Bs. Retransmissions are generateduntil successful transmission is realized by at least one of theNode-Bs. Successful transmission is not guaranteed at all of theNode-Bs. Therefore, since a complete set of successful transmissions maynot be available within any one Node-B, re-ordering of successfultransmissions cannot be accomplished.

SUMMARY

The present invention is related to a method and apparatus forprocessing data blocks during soft handover. The apparatus may be awireless communication system, a radio network controller (RNC) or anintegrated circuit (IC). The wireless communication system includes atleast two enhanced uplink soft handover (EU-SHO) Node-Bs and an RNC.Each Node-B decodes a received data block and forwards the decoded datablock to the RNC with an indication of a decoding result, i.e., a cyclicredundancy check (CRC). If the RNC receives at least one copy of asuccessfully decoded data block, the RNC uses a re-ordering functionentity to process successfully decoded data blocks to providein-sequence delivery to higher protocol layers. If the RNC receives morethan one copy of a successfully decoded data block, the RNC discards theextra successfully decoded data block copies. The RNC is either aserving-RNC (S-RNC) or a controlling-RNC (C-RNC). Each Node-B includes amedium access control (MAC) entity that handles enhanced uplinkdedicated channel (EU-DCH) functionalities.

BRIEF DESCRIPTION OF THE DRAWING(S)

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way ofexample, and to be understood in conjunction with the accompanyingdrawings wherein:

FIG. 1 is a block diagram of a wireless communication system forprocessing data blocks in a serving-RNC in accordance with a preferredembodiment of the present invention;

FIG. 2 is a flowchart of a process including method steps for processingdata blocks in the system of FIG. 1;

FIG. 3 is a block diagram of a wireless communication system forprocessing data blocks in a controlling-RNC in accordance with analternate embodiment of the present invention; and

FIG. 4 is a flowchart of a process including method steps for processingdata blocks in the system of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The present invention will be described with reference to the drawingfigures wherein like numerals represent like elements throughout.

Hereafter, the terminology “WTRU” includes but is not limited to a userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “base station”includes but is not limited to a Node-B, a site controller, an accesspoint or any other type of interfacing device in a wireless environment.

The present invention may be further applicable to TDD, FDD, and timedivision synchronous code division multiple access (TD-SCDMA), asapplied to UMTS, CDMA 2000 and CDMA in general, but is envisaged to beapplicable to other wireless systems as well. With respect to CDMA2000,the present invention may be implemented in EV-DO (i.e., data only) andEV-DV (i.e., data and voice).

The features of the present invention may be incorporated into an IC orbe configured in a circuit comprising a multitude of interconnectingcomponents.

During soft handover, higher layers maintain an active subset of EUcells for which EU-DCHs are maintained in a soft handover macrodiversity state. Those cells in the active subset may be controlled bydifferent EU-SHO Node-Bs.

FIG. 1 shows a wireless communication system 100 including an S-RNC 105and at least two (2) EU-SHO Node-Bs 110 (110A . . . 110N) operating inaccordance with a preferred embodiment of the present invention. One ormore re-ordering function entities 115 are implemented at the S-RNC 105for each WTRU with and without soft handover. The HARQ or ARQ processesfor handling EU-DCH functionalities are located in a MAC entity 120located within each respective EU-SHO Node-B 110. Each re-orderingfunction entity 115 communicates with higher protocol layers 125 withinthe S-RNC 105 and includes an associated data buffer (not shown).

FIG. 2 is a flowchart of a process 200 including method steps forprocessing data blocks, i.e., packet data units (PDUs), in the system100 during a soft handover. In step 205, a data block, (i.e., an EU datablock), is received at each EU-SHO Node-B 110 from a WTRU. In step 210,each EU-SHO Node-B 110 decodes the received data block, and the decodeddata block is forwarded to the S-RNC 105. It should be noted that eachEU-SHO Node-B 110 will attempt to decode received EU transmissions. Whenthere is a CRC error, the EU-SHO Node-B 110 cannot forward the receiveddata block to the S-RNC 105, unless the identity of the WTRU and logicalchannel/MAC-d flow is known by other means. All successfully decodedblocks with good CRC check results are forwarded to the S-RNC 105.

Still referring to FIG. 2, a determination is made as to whether or notat least one copy of a successfully decoded data block is received bythe S-RNC 105 from an EU-SHO Node-B 110 (step 215). If it is determinedin step 215 that the S-RNC 105 has not received any copy of asuccessfully decoded data block, the forwarded data block is regarded asnot having been correctly received (step 220). If, in step 215, it isdetermined that at least one copy of a successfully decoded data blockhas been received by the S-RNC 105 from an EU-SHO Node-B 110, adetermination is then made as to whether or not multiple copies of thesuccessfully decoded data block are received from different EU-SHONode-Bs 110 (step 225).

If step 225 determines that multiple copies of the successfully decodeddata block are received from different EU-SHO Node-Bs 110, only one copywill be stored in a re-ordering buffer (not shown) maintained by are-ordering function entity 115 in the S-RNC 105 as a correctly receiveddata block, and any extra received copies of the successfully decodeddata block are discarded as redundant data (step 230).

Finally, in step 235, the successfully decoded data block is processedby the re-ordering function entity 115 in the S-RNC 105. The re-orderingfunction entity 115 in the S-RNC 105 performs a re-ordering procedure onthose successfully decoded data blocks that are correctly received inthe re-ordering function entity 115 so as to support in-sequencedelivery to the higher protocol layers 125.

Process 200 is beneficial because data blocks received from differentEU-SHO Node-Bs 110 can be combined and organized in-sequence fordelivery to the higher protocol layers 125 of the S-RNC 105. There-ordering function entity 115 located within the S-RNC 105 allowsenhanced uplink MAC PDU's to be processed for successful reception andproper delivery to higher layers independent of which Node-B(s) thatprovided reception of each PDU, resulting in the reduction of loss ofMAC data and RLC recoveries.

FIG. 3 shows a wireless communication system 300 including a C-RNC 305and at least two (2) EU-SHO Node-Bs 110 (110A . . . 110N) operating inaccordance with an alternate embodiment of the present invention. One ormore re-ordering function entities 315 are implemented at the C-RNC 305for support of soft handover. The HARQ or ARQ processes for handlingEU-DCH functionalities are located in a MAC entity 320 located withineach respective EU-SHO Node-B 310. Each re-ordering function entity 315communicates with higher protocol layers 325 external to the C-RNC 305and includes an associated buffer (not shown).

FIG. 4 is a flowchart of a process 400 including method steps forprocessing data blocks, i.e., PDUs, in the system 300 during a softhandover. In step 405, a data block (i.e., an EU data block) is receivedat each EU-SHO Node-B 310 from a WTRU. In step 410, each EU-SHO Node-B310 decodes the received data block, and the decoded data block isforwarded to the C-RNC 305. It should be noted that each EU-SHO Node-B310 will attempt to decode received EU transmissions. When there is aCRC error, the EU-SHO Node-B 310 cannot forward the received data blockto the C-RNC 305, unless the identity of the WTRU and logicalchannel/MAC-d flow is known by other means. All successfully decodedblocks with good CRC check results are forwarded to the C-RNC 305.

Still referring to FIG. 4, a determination is made as to whether or notat least one copy of a successfully decoded data block is received bythe C-RNC 305 from an EU-SHO Node-B 310 (step 415). If it is determinedin step 415 that the C-RNC 305 has not received any copy of asuccessfully decoded data block, the decoded data block forwarded by theEU-SHO Node-Bs 310 is regarded as not having been correctly received(step 420).

If, in step 415, it is determined that at least one copy of asuccessfully decoded data block has been received by the C-RNC 305 froman EU-SHO Node-B 310, a determination is then made as to whether or notmultiple copies of the successfully decoded data block are received fromdifferent EU-SHO Node-Bs 110 (step 425).

If step 425 determines that multiple copies of the successfully decodeddata block are received from different EU-SHO Node-Bs 310, only one copywill be stored in a re-ordering buffer (not shown) maintained by are-ordering function entity 315 in the C-RNC 305 as a correctly receiveddata block, and any extra received copies of the successfully decodeddata block are discarded as redundant data (step 430).

Finally, in step 435, the successfully decoded data block is processedby the re-ordering function entity 315 in the C-RNC 305, which performsa re-ordering procedure on those successfully decoded data blocks thatare correctly received in the re-ordering function entity 315 so as tosupport in-sequence delivery to the higher protocol layers 325.

Process 400 is beneficial because data blocks received from differentEU-SHO Node-Bs 310 can be combined and organized in sequence fordelivery to the higher protocol layers 325, provided that these Node-Bs310 have the same C-RNC 305. This is frequently the case, although itsapplicability is somewhat more restrictive than placing a re-orderingfunction in an S-RNC 105. However, this restriction is offset by otherconsiderations. For example, a benefit of C-RNC operation is reducedlatency for H-ARQ operation. The performance benefits of minimizing thislatency are well understood in the art. During soft handover, it is alsodesirable to have a common uplink scheduler in the C-RNC 305 for all ofthe cells that are in the active EU subset, including cells that arecontrolled by different Node-Bs 310.

While this invention has been particularly shown and described withreference to preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the scope of the invention describedhereinabove. * * *

1. In a wireless communication system including at least two Node-Bs anda radio network controller (RNC) including a re-ordering functionentity, a method for processing data blocks during soft handover, themethod comprising: (a) each Node-B decoding a received data block andforwarding the decoded data block to the RNC; and (b) if the RNCreceives at least one copy of a successfully decoded data block from theNode-Bs, the RNC using the re-ordering function entity to process thecopy of the successfully decoded data block to support in-sequencedelivery to higher protocol layers.
 2. The method of claim 1 whereinstep (b) further comprises: (b1) if the RNC receives more than one copyof a successfully decoded data block from the Node-Bs, the RNCdiscarding the extra successfully decoded data block copies.
 3. Themethod of claim 1 wherein the RNC is a serving-RNC (S-RNC) and thehigher protocol layers are located within the S-RNC.
 4. The method ofclaim 1 wherein the RNC is a controlling RNC (C-RNC) and the higherprotocol layers are located external to the C-RNC.
 5. The method ofclaim 1 wherein each Node-B is an enhanced uplink soft handover (EU-SHO)Node-B.
 6. The method of claim 1 wherein each Node-B includes a mediumaccess control (MAC) entity that handles enhanced uplink dedicatedchannel (EU-DCH) functionalities.
 7. A wireless communication system forprocessing data blocks during soft handover, the system comprising: (a)at least two Node-Bs; and (b) a radio network controller (RNC) incommunication with the Node-Bs, the RNC including a re-ordering functionentity, wherein each Node-B decodes a received data block and forwardsthe decoded data block to the RNC, and if the RNC receives at least onecopy of a successfully decoded data block from the Node-Bs, the RNC usesthe re-ordering function entity to process the copy of the successfullydecoded data block to support in-sequence delivery to higher protocollayers.
 8. The system of claim 7 wherein if the RNC receives more thanone copy of a successfully decoded data block from the Node-Bs, the RNCdiscards the extra successfully decoded data block copies.
 9. The systemof claim 7 wherein the RNC is a serving-RNC (S-RNC) and the higherprotocol layers are located within the S-RNC.
 10. The system of claim 7wherein the RNC is a controlling RNC (C-RNC) and the higher protocollayers are located external to the C-RNC.
 11. The system of claim 7wherein each Node-B is an enhanced uplink soft handover (EU-SHO) Node-B.12. The system of claim 7 wherein each Node-B includes a medium accesscontrol (MAC) entity that handles enhanced uplink dedicated channel(EU-DCH) functionalities.
 13. A radio network controller (RNC) forprocessing data blocks forwarded to the RNC by at least two Node-Bsduring soft handover, the RNC comprising: (a) at least one re-orderingfunction entity; (b) higher protocol layers; and (c) means for receivingat least one copy of a successfully decoded data block from the Node-Bs,wherein the RNC uses the re-ordering function entity to process the copyof the successfully decoded data block to support in-sequence deliveryto the higher protocol layers.
 14. The RNC of claim 13 furthercomprising: (d) means for discarding extra copies of a successfullydecoded data block received from the Node-Bs.
 15. The RNC of claim 13wherein the RNC is a serving-RNC (S-RNC).
 16. The RNC of claim 13wherein each Node-B is an enhanced uplink soft handover (EU-SHO) Node-B.17. The RNC of claim 13 wherein each Node-B includes a medium accesscontrol (MAC) entity that handles enhanced uplink dedicated channel(EU-DCH) functionalities.
 18. A radio network controller (RNC) forprocessing data blocks forwarded to the RNC by at least two Node-Bsduring soft handover to support in-sequence delivery to higher protocollayers external to the RNC, the RNC comprising: (a) at least onere-ordering function entity; and (b) means for receiving at least onecopy of a successfully decoded data block from the Node-Bs, wherein theRNC uses the re-ordering function entity to process the copy of thesuccessfully decoded data block.
 19. The RNC of claim 18 furthercomprising: (c) means for discarding extra copies of a successfullydecoded data block received from the Node-Bs.
 20. The RNC of claim 18wherein the RNC is a controlling-RNC (C-RNC).
 21. The RNC of claim 18wherein each Node-B is an enhanced uplink soft handover (EU-SHO) Node-B.22. The RNC of claim 18 wherein each Node-B includes a medium accesscontrol (MAC) entity that handles enhanced uplink dedicated channel(EU-DCH) functionalities.
 23. An integrated circuit (IC) for processingdata blocks received from a plurality of data sources, the ICcomprising: (a) at least one re-ordering function entity; (b) higherprotocol layers; and (c) means for receiving at least one copy of asuccessfully decoded data block from the data sources, wherein the ICuses the re-ordering function entity to process the copy of thesuccessfully decoded data block to support in-sequence delivery to thehigher protocol layers.
 24. The IC of claim 23 further comprising: (d)means for discarding extra copies of a successfully decoded data blockreceived from the data sources.
 25. The IC of claim 23 wherein each datasource is an enhanced uplink soft handover (EU-SHO) Node-B.
 26. The ICof claim 23 wherein each data source includes a medium access control(MAC) entity that handles enhanced uplink dedicated channel (EU-DCH)functionalities.
 27. The IC of claim 23 wherein the IC is located in aserving radio network controller (S-RNC) that processes data blocksforwarded to the S-RNC by the data sources during soft handover.
 28. Anintegrated circuit (IC) for processing data blocks received from aplurality of data sources, the IC comprising: (a) at least onere-ordering function entity; and (b) means for receiving at least onecopy of a successfully decoded data block from the data sources, whereinthe IC uses the re-ordering function entity to process the copy of thesuccessfully decoded data block to support in-sequence delivery toexternal higher protocol layers.
 29. The IC of claim 28 furthercomprising: (c) means for discarding extra copies of a successfullydecoded data block received from the data sources.
 30. The IC of claim28 wherein each data source is an enhanced uplink soft handover (EU-SHO)Node-B.
 31. The IC of claim 28 wherein each data source includes amedium access control (MAC) entity that handles enhanced uplinkdedicated channel (EU-DCH) functionalities.
 32. The IC of claim 28wherein the IC is located in a controlling radio network controller(C-RNC) that processes data blocks forwarded to the C-RNC by the datasources during soft handover.
 33. In a wireless communication systemincluding a plurality of Node-Bs and a plurality of wirelesstransmit/receive units (WTRUs) configured for enhanced uplink (EU)services, a radio network controller (RNC) for processing data blocksforwarded to the RNC by at least two of the Node-Bs during soft handoverto support in-sequence delivery to higher protocol layers external tothe RNC, the RNC comprising: (a) a plurality of re-ordering functionentities, wherein at least one of the re-ordering function entities isassociated with each of the plurality of WTRUs; and (b) means forreceiving at least one copy of a successfully decoded data block fromthe Node-Bs, wherein the RNC uses the at least one re-ordering functionentity to process the copy of the successfully decoded data block. 34.The RNC of claim 33 further comprising: (c) means for discarding extracopies of a successfully decoded data block received from the Node-Bs.35. The RNC of claim 33 wherein the RNC is a controlling-RNC (C-RNC).36. The RNC of claim 33 wherein each Node-B is an enhanced uplink softhandover (EU-SHO) Node-B.
 37. The RNC of claim 33 wherein each Node-Bincludes a medium access control (MAC) entity that handles enhanceduplink dedicated channel (EU-DCH) functionalities.